This project involves the conduct of therapeutic clinical trials for the treatment of inherited immune deficiencies using hematopoietic stem cell transplantation. We previously reported the successful use of non-ablative conditioning to achieve successful long-term engraftment and cure of CGD patients using HLA-matched sibling donors as the source of the hematopoietic stem cell graft. One of the problems with this approach was the high rate (30%) of graft failure or very low engraftment. In 2004 we performed a follow up transplant on an X-CGD child previously transplanted by us who had achieved high level donor T cell engraftment but less than 1% long term myeloid engraftment. We demonstrated successful permanent conversion to almost 100% donor chimerism in the lymphoid and myeloid lineages using conditioning with only busulfan at 10 mg/kg. This strongly supports the use of this approach to rescue low engraftment rather than using a fully myelo- and lympho-ablative conditioning regimen for such salvage therapy. In 2007 we initiated a clinical protocol using busulfan, Campath and low dose TBI and treated 44 patients with CGD, 39 of whom received an unrelated donor graft. and the results were published in the Journal of Clinical Immunology. (Parta et al. JCI). Overall our results for the CGD patients in particular are especially promising with an overall survival of 38 out of 47 and an overall long term engraftment rate of 35 out of 38 evaluable. We are also the only centre to have transplanted patients with the P40 form of CGD demonstrating complete reversal of refractory colitis in this unique subset. In follow up to that study we have opened a new protocol modeling on our previous results using a higher cell dose and post-transplant cyclophosphamide to mitigate the increased risk of GvHD from the higher cell dose. At this point, we have enrolled 16 patients on this protocol with three patients dying due to progressive pulmonary disease. Patient one died 2 days after receiving his cells due to progression of his underlying pneumonitis and pneumonia. Patient 8 died 27 days after cell infusion with multiorgan failure secondary to engraftment syndrome overlying progression of his pulmonary disease. A second patient also developed significant engraftment syndrome and died. A retrospective evaluation of all transplanted patients suggested that underlying inflammation with an elevated CRP prior to the transplant itself was the one common risk factor and the protocol was therefore modified to exclude patients who have an elevated CRP just prior to conditioning. We have subsequently transplanted 3 more patients with good outcomes since those two deaths. One patient did not receive the post-transplant cyclophosphamide due to a low cell dose and although he had initial engraftment, he eventually lost the graft at day 85. He remains alive and well. The remainder of the patients have all done well with one patient developing grade1 GvHD limited to the skin and a second patient developing Grade 2 GvHD of the gut precipitated by a rotavirus infection contracted while in hospital prior to his transplant. At the end of 2014, we also initiated a clinical trial using haploidentical donors and transplanted a patient with no matched donors available. This patient had an ongoing infection refractory to all standard therapy involving the heart and we therefore proceeded with a parental graft and using post-transplant cyclophosphamide. We obtained good engraftment with only limited graft versus host disease. This patient is now almost 2 years out with complete resolution of his infection and has been described in publication. (J Clin Immunol. 2015 Oct;35(7):675-80). We enrolled a total of 7 patients on this protocol but experienced severe GvHD in the last three patients with two of the patients succumbing to complications related to GvHD. The third patient is doing well having recovered from the GvHD. A manuscript is in preparation describing these results, to be submitted this year. This protocol is now closed and a new protocol has been designed and is now open (19-I-0080). This new study uses both early and late Campath along with the busulfan and TBI along with post transplant cyclophosphamide. In order to determine the outcomes of transplant for CGD in general, we have become a part of the Primary Immune Deficiency Treatment Consortium ( J Allergy Clin Immunol. 2014 Feb;133(2):335-47) and have initiated a collaborative protocol to review the results of transplant done for CGD in North America. We have enrolled over 100 previously transplanted patients and have presented data on a subgroup of patients with inflammatory bowel disease at both the ASBMT and the CIS meetings. We have now published the results of this substudy (JCI, Marsh et al) and are now in the midst of compiling and analyzing the data from the overall study. We have also been obtaining stool samples pre and post-transplant for microbiome analysis, another sub-study being done in collaboration with Emilia Falcone (NIAID) and Julie Segre (NHGRI). This microbiome data was presented at both ESID and at the CIS meeting this year and a manuscript is now in preparation. The PIDTC also submitted a grant proposal to continue the consortium this year which has been funded and we are in the midst of finalizing a new CGD related protocol- 6908 in conjunction with this grant, which will evaluate in more detail, the autoinflammatory aspects of CGD in patients pre and post-transplant. In related laboratory pre-clinical studies, we had been investigating the use of an adenosine A2a receptor agonist to prevent or treat graft versus host disease (GVHD). However the company has discontinued production and support of these agonists. We are therefore looking into other avenues as these were very promising biological compounds. A commercial version, approved for cardiac imaging is too non-specific and is not effective in our models but does provide data that these compounds would probably be well tolerated. We also had a collaboration with Gabriel Dvesklar of UHSUS to study Pregnancy Specific Glycoprotein -1 (PSG-1) as an immunomodulator and a possible therapy for GvHD and we have published two papers in collaboration using our murine models. Limitations to clinical application though include production of these specific proteins on a clinical scale. Caroline Kreitzer, a post baccalaureate in the laboratory, was working with the A2a receptors, but given the obstacles with obtaining more compound for testing has not been able to continue with this project. She is now in the midst of developing a graft rejection model, assessing the cytokine profiles of engraftment and rejection to help determine the pathways responsible for graft failure, a significant complication that appears to be more frequent in CGD compared to other immunodeficiencies.